138 A MANUAL OF PHYSIOLOGY 



In the case of the warm-blooded heart a complete breakdown 

 of co-ordination occurs under certain circumstances, producing 

 the phenomenon known as fibrillary contraction, or delirium 

 cordis, a condition in which each minute portion, perhaps each 

 fibre, of the whole heart, or of a portion of it, goes on contracting 

 in a disorderly manner, quite independently of the rest. The 

 condition is often seen in a heart that has been exposed for some 

 time, particularly in the ventricle, and can be induced by stimu- 

 lating it with strong induction shocks or by ligation of the coronary 

 arteries. There is no reason to believe that fibrillary contraction 

 is connected with the loss of impulses from any special co-ordinat- 

 ing centre, for it is not peculiar to the heart, but is typically seen 

 in the tongue when the circulation after a long interruption is 

 restored. The peculiar ' boiling ' movement is exactly similar 

 to that observed in the heart, probably because the tongue also 

 contains fibres running in several directions. 



Without entering further into a discussion of the rival hypo- 

 theses, we may sum up by saying that for one heart (that of 

 Ltmulus) the automatism and the rhythmical power have been 

 clearly shown to reside in the local nervous apparatus ; for the hearts 

 of other animals full and formal proof of the neurogenic theory, so 

 far as those two properties of the cardiac tissue are concerned, has 

 not been given. It is probable, but not proven. As regards the 

 conduction and co-ordination of the contraction, the bulk of the 

 evidence (leaving the Limulus heart out of account] points to the 

 muscular tissue as the channel through which the effective impulses 

 pass. The normal order or sequence in which the different parts 

 of the heart contract depends upon the fact that the automatism of 

 the upper portions is more pronounced than that of the lower, so 

 that under strictly physiological conditions the contraction is only 

 propagated, and not originated, by the lower parts of the heart. When, 

 however, the signal to contraction normally given by the basal 

 region is prevented from reaching the lower parts, an independent 

 automatic rhythm of the latter may be developed, as in the case 

 of the mammalian ventricle mentioned above. Here we may 

 suppose that the automatic mechanism of the lower portions of 

 the heart discharges itself as soon as a sufficient accumulation 

 of energy has taken place in it, although it requires a longer 

 time to reach the point of discharge than the automatic 

 mechanism of higher parts, and therefore is normally dis- 

 charged from above. Under certain conditions the normal 

 sequence can be reversed. In the heart of the skate it is 

 easy, by stimulating the bulbus arteriosus, to cause a con- 

 traction passing from bulbus to sinus. The power of propa- 

 gating the contraction may also be artificially altered. As 

 already mentioned, it may be diminished or abolished by 



